Purpose/Significance of Application:Combined use of groundwater pump and treat and SVE to remediate TCE and DNAPLs

Regulatory Requirements/Cleanup Goals:
- Groundwater - reduce VOC concentrations to MCLs in all contaminated groundwater including a cleanup goal of 5 mcg/L for TCE. The discharge limit is 0.5 mcg/L for total VOCs.
- Soil - soil vapor of 0.36 ppmv; soil vapor remediation will continue until: 1) it is demonstrated that VOC removal from the vadose zone is no longer technically or economically feasible and 2) the VOC inhalation risk inside Building 875 is adequately managed.

Results:- Maximum TCE groundwater concentrations had been reduced from pre-remediation levels ranging from as high as 240,000 mcg/L at the site to levels of 13 mcg/L (eastern GSA) and 33 mcg/L (central GSA) as of May 1997. These levels are above the cleanup goal of 5 mcg/L.
- Maximum TCE soil vapor concentrations had been reduced from a pre-remediation level of 450 ppmv to 2 ppmv as of May 1997, above the cleanup goal of 0.36 ppmv. - The discharge limits have been met while the system was operating.

Cost Factors:Total cost for GSA OU - $36.6 million, including $6.2 million for the Eastern GSA P&T and $32.4 million for the Total Central GSA P&T and SVE systems. The costs include preconstruction and construction activities and post-construction O&M.

Description:Lawrence Livermore National Laboratory Site 300 is a DOE experimental test facility located near Livermore California. Craft shops and equipment fabrication and repair facilities in the General Services Area (GSA) used solvents as degreasing agents. In the eastern portion of the GSA, craft shop debris was buried in shallow trenches. In the central portion, rinse waters from operations were disposed of in dry wells. The results of site investigations, begun in 1982, identified VOC contamination in the soil and groundwater. Groundwater TCE concentrations have been detected as high as 74 ug/L in the eastern GSA and 240,000 mcg/L in the central GSA. Groundwater TCE plumes have been identified in both areas. The highest pre-remediation concentration of TCE in soil in the central GSA were 360,000 mcg/L. Remediation began in 1991 as a removal action. A Record of Decision was signed moving the cleanup to the remedial phase.

The remedy at the eastern portion of the GSA, begun in 1991, involves groundwater extraction using three wells and treatment using carbon adsorption. The system originally used air sparging; however, as VOC concentrations in the groundwater decreased, air sparging was replaced with carbon adsorption. After six years of operation, the system has removed 5.1 kg of VOC mass, treated 93 million gallons of groundwater and reduced the maximum TCE concentration in groundwater to 13 mcg/L. The remedy for the central portion of the GSA included both groundwater extraction and treatment and SVE. The groundwater system, operated since 1993, had 19 extraction wells and includes air stripping for vapors and carbon adsorption for treatment of groundwater. After four years of operation, the system has removed 4.8 kg of VOC mass, treated 787,000 gallons of groundwater, and reduced maximum TCE levels to 33 mcg/L. The SVE system, operated since 1993, has removed 30.5 kg of VOC mass and reduced TCE concentrations in the soil vapor to 2 ppmv. Levels of VOC remained above the cleanup goals as of 1997. Cyclic pumping is used to maximize VOC mass removal efficiency from all three systems. Results of modeling used to predict the timeframe for cleanup indicated that the SVE system would require 10 years and groundwater extraction and treatment 55 years.

The total cost for the three technologies at the GSA OU as of 1997 is $36.6 million. This includes preconstruction and construction activities and post-construction O&M. The costs for the Eastern GSA P&T system is $6.2 million. The cost for the Central GSA P&T and SVE systems is $32.4 million.